Method for using a mixture of fluorinated hydrocarbons as a refrigerant, and a refrigeration unit using the mixture as a refrigerant

Abstract

The present invention provides a method for using, as an alternative refrigerant for R404A that is currently widely used, a refrigerant that has, for example, a non-flammability similar to that of R404A, a refrigerating capacity that can replace that of R404A, a COP equal or superior to that of R404A, and a lower GWP than that of R404A, as a refrigerant for a cooling system; as well as a refrigeration unit using the refrigerant. The method uses a mixture of fluorinated hydrocarbons as a refrigerant, (1) the mixture comprising difluoromethane (R32), pentafluoroethane (R125) and 1,1,1,2-tetrafluoroethane (R134a) in amounts such that the sum of the concentrations thereof is 99.5 wt % or more; (2) the composition ratio of the fluorinated hydrocarbons contained in the mixture falling within a triangle having, as vertices, the following three points in a ternary composition diagram in which the sum of the concentrations of R32, R125, and R134a is 100 wt %, point A (R32/R125/R134a=37.3/17.0/45.7 wt %), point F (R32/R125/R134a=30.7/10.9/58.4 wt %), and point G (R32/R125/R134a=29.4/14.1/56.5 wt %); and (3) the mixture being used as a refrigerant in a cooling system comprising a heat exchanger in which a flow of the refrigerant and a flow of an external heat medium are counter flows.